Conventional analyzers have been constructed to provide some level of climate control in parts thereof. The most frequent climate control is temperature control provided in the incubator, that is, in the portion where test samples are reacting with reagents prior to a reading being made at a detecting station. Such temperature control can include means for blowing air over the samples and over heating elements, as shown, for example, in U.S. Pat. Re. 30,730 and U.S. Pat. No. 3,616,264.
It has also been known that climate control is equally important in the storage area or supplying means of test elements, particularly when so-called "dried" slide like test elements are used. For example, analyzers have been known to provide a desiccant inside a cartridge, adjacent a plurality of such test elements while stored, as in Japanese Kokai No. 62/030962. However, this is not acceptable in analyzers having a large storage area for test elements prior to sample addition. That is, some of the other test elements may require moistening air, which would be deleterious to such desiccants. For example, test elements for the assays of total protein, magnesium, albumin and calcium need a high relative humidity of about 33%, whereas those for the assays of LDH, CK, AST and gamma glutamyltransferase need only 15%.
Yet another approach, currently used in analyzers available under the trademark "Ektachem 700" analyzers from Eastman Kodak Company, is to provide two separate storage areas of cartridges. In one area, those that prefer to be stored under dry conditions have a desiccant stored with them. This is the only humidity control, that is, it removes moisture only, and does so passively. In the other storage area, cartridges are placed that prefer a higher degree of relative humidity, and a salt pad capable of adding or removing moisture within a range is present. In this other area, the addition of moisture is passive only--there is no attempt to make the air in the storage area more uniform in content.
Although such a system has provided control of the relative humidity, there have been instances in which better and more rapid control was needed. For example, test elements and cartridges stored with only a desiccant present can become too dry when used in, e.g., desert conditions. The problem with the storage atmosphere being too dry is that it induces reduced storage life.
Thus, it has been discovered that conditions can be experienced in which both water addition and deletion are required, alternately, to the atmosphere of the storage area, over a period of time. Merely storing a drying means or a wetting means in a cartridge or its storage area does not permit a rapid opposite change in the relative humidity in such a cartridge, particularly when such means are passive only, as defined herein.
Accordingly, it has been a problem prior to this invention that the storage area or supplying means for slide like test elements has not been able to provide the proper relative humidity for storage that each kind of test element needs. A further problem is that control of such relative humidity has been cumbersome.